Flexible smoke expansion chamber



Oct. 11, 1966 G. E. CHILDS ETAL FLEXIBLE SMOKE EXPANSION CHAMBER 2Sheets-Sheet 1 Filed Nov. 14, 1963 FIG.

TO m COATING POSIHON FIG.2.

INVENTORS. GORDON 5.6711405 41 T/I/YLEY H. LOPEN5K/. BY \7 7 Arm/awn.

Oct. 11, 1966 G. E. CHILDS ETAL 3, 78,

FLEXIBLE SMOKE EXPANSION CHAMBER 2 Sheets-Sheet 2 Filed NOV. 14, 1965INVENTOR5 60/200 E. CH/LDS r1 FIG. 8.

STHNLEY H. LOPEN$/f/.

FIG.6.

T0 COATWG POSIT\ON To SMOKE GENERATOR.

POSITION TO 2nd. COAT1N6 To \fit com-me posmow FIG. 5.

United States Patent 3,278,451 FLEXIBLE SMOKE EXPANSION CHAMBER GordonE. Childs and Stanley A. Lopenslti, Pompton Plains, N.J., assignors toWestinghouse Electric Corporation, East Pittsburgh, Pa, a corporation ofPennsylvania Filed Nov. 14, I963, Ser. No. 323,727 4 Claims. (Cl.252-359) The present invention relates to electrostatic coatingapparatus and more particularly to such apparatus for supplying powdersuspended in a gaseous medium such as air to the interior of anincandescent lamp bulb to apply a coating thereto.

Electrostatic coating apparatus of this general nature is now Well knownto the art with one such apparatus for simultaneously coating aplurality of incandescent lamp bulbs with a powdered light diffusingcoating being shown in US. Patent No. 3,017,852, as well as in ourpending US. application, Serial No. 303,821, filed August 22, 1963, bothassigned to the same assignee as the present invention. One of the mostsalient difficulties with this electrostatic coating apparatus hasheretofore resided in the fact that the swirling dry powder creates astatic charge causing agglomerates to form and adhere to the wall of therigid expansion chamber during successive coating cycles. Such repeatedcycles tend to increase this powder build-up to the point where theweight overcomes the charge on the powder particles causing periodicdislodgment thereof. This dislodgment in turn detrimentally affects thecoating density of the lamp bulbs by supplying too much or too littlepowder, depending upon the moment of dislodgment of the agglomeratesduring the coating cycle.

It is accordingly the primary object of the present invention to providean electrostatic coating apparatus for generating a powder-smoke andapplying the powder therefrom to the surface of an electric lamp bulband wherein the formation of powder agglomerates in the expansionchamber during operation of such apparatus is minimized.

Another object of the present invention is the provision of anelectrostatic coating apparatus for applying a coating to an electriclamp bulb from a powder-smoke and wherein a flexible expansion chamberis utilized as part of such apparatus to eliminate the build-up ofpowder agglomerates which otherwise affect the density of the appliedcoating.

The foregoing objects of the present invention, together with otherobjects which will become apparent from the following description, areaccomplished by providing an expansion chamber which so expands andcontracts during the bulb coating cycles that any tendency towardbuild-up of powder agglomerates on the wall of such expansion chamber isminimized or eliminated by dis lodgment thereof before any appreciableagglomerate formation can occur. Accordingly, by preventing theformation of such agglomerates, which otherwise are eliminated onlythrough dislodgment due to their own weight, the density of theresulting coating is maintained more uniform.

The present invention may be more readily understood by reference to theaccompanying drawings wherein:

FIGURE 1 is an elevational view in cross-section of the expansionchamber forming part of the electrostatic coating apparatus inaccordance with the present invention,

FIG. 2 is a cross-sectional view taken on the line IIII of FIG. 1,

FIG. 3 is a fragmentary sectional view in elevation taken on the lineIIIIII of FIG. 1,

3,278,4l5l Patented Get. 11, 1966 FIG. 4 is a cross-sectional view takenon the line IVIV of FIG. 1,

FIG. 5 is an elevational view in cross-section of the expansion chamberas shown in FIG. 1 but flexed to its expanded position during the actualcoating cycle,

FIG. 6 is a cross-sectional view taken on the line VIVI of FIG. 5,

FIG. 7 is an elevational view in cross-section of a modification whichthe expansion chamber of the electrostatic coating apparatus of thepresent invention may take,

FIG. 8 is a sectional view taken on the line VIIIVIII of FIG. 7,

FIG. 9 is a cross-sectional view similar to that of the modificationshown in FIG. 7 but taken at ninety degrees relative to the latter, and

FIG. 10 is a cross-sectional view taken on the line XX of FIG. 7.

Referring now more specifically to FIG. 1, the portion of theelectrostatic coating apparatus as shown therein is similar to thatdisclosed and claimed in pending application, Serial No. 227,489, filedOctober 1, 1962 and assigned to the same assignee as the presentinvention, and hence further detailed description thereof is deemedunnecessary herein. Suffice it to say that, like such previouslydisclosed electrostatic apparatus, the present invention also comprisesa smoke generator 5 which is fed with powder through a conduit 6extending from the usual powder drum (not shown). Upon operation of asuitable electrically controlled valve 7 dry air is supplied from asuitable source, as indicated by the legend, through a conduit 8 andventuri 9. The air-suspended powder particles in the form of smoke areremoved from the smoke generator 5 by the venturi action and are carriedthrough a further conduit 10 into the interior of an expansion chamber12.

This expansion chamber 12, as shown more in detail in FIGS. 1 and 3,comprises a metallic casing, or the like, 13 of graduated volume andprovided with a coaxially disposed expansible tubular insert 14 ofrubber or resilient plastic composition properly sealed to the expansionchamber 12 at the top and bottom thereof by usual type packing collarsor the like as shown. Since the conduit 10 communicates directly withthe interior of the expansible tubular insert 14 through an acceleratingvalve 15, which may be of the type shown and claimed in our aforesaidpending application, Serial No. 303,821, a swirling accelerated motionis imparted to the smoke particles as they enter this expansible tubularinsert 14. The casing 13 of the expansion chamber 12, upon operation ofan electrically operated valve 16, is subject to an air supply through aconduit 17 and differential venturi 18, the latter of which exhausts tothe atmosphere. Accordingly, during the actual coating cycle when boththe valves 7 and 16 are electrically opened, the pressure build-up ofthe swirling smoke powder entering the expansible tubular insert 14together with the suction exerted thereon by the action of the airflowing through conduit 17 and differential venturi 18, causes thisresilient insert 14 to expand until it contacts the interior wall of thecasing 13 and assumes the contour thereof, as shown in FIGS. 5 and 6.

Simultaneously with expansion of the insert 14 the smoke powder isforced by the pressure thereof upwardly through the conduits 19 and 20which extend to first and second position coating manifolds,respectively, for the application of an initial electrostatic coating,as well as a second such coating at another position when desired, to agroup of electric lamp bulbs as disclosed in our above-mentioned pendingapplication, Serial No. 303,821. During the coating cycle when theresilient tubular insert 14- is completely expanded the bottom thereofis sealedolf by a resilient pinch valve 22, as shown by the dotted 3lines in FIG. 1 and by the full lines of FIG. 5, of the type disclosedand claimed in our prior Patent No. 2,884,895, granted May 5, 1959 andassigned to the same assignee as the present invention.

Upon completion of the actual coating cycle the electrically operablevalves 7 and 16 are closed causing the pinch valve 22 to open, due torelease of air pressure formerly exerted from conduit 17, andsimultaneously the expanded resilient insert 14 collapses due tocessation of pressurized smoke from the smoke generator through conduit10 and the removal of the suction action from differential venturi 18.Inasmuch as the expansible tubular insert 14 is of rubber or plasticcomposition and hence of a dielectric material, there is substantiallyno electrostatic charge build-up on the walls thereof which contributesto minimizing the accumulation of powder agglomerates thereon. This isfurther minimized in accordance with the present invention by theexpansion and collapsing of the resilient tubular insert which itselfdislodges any powder normally adhering to the surface immediately aftereach coating cycle and hence all excess powder remains unchanged indensity. Immediately following opening of the pinch valve 22 blow backair is introduced into the system which enters the expansion chamber 12through one or both of the conduits 19 and 20 and thus removes excesspowder through a reclaim venturi and conduit system and delivers it backto the powder supply drum as more fully shown and described in ouraforesaid Patent No. 2,884,895.

The modification of the present invention, as shown in FIGS. 7 and 10,differs from that previously described herein by the elimination of themetallic casing 13 with the expansion chamber 32 itself being formedentirely of the same expansible dielectric material as previouslymentioned relative to the expansible tubular insert 14. In suchmodification it is preferable, however, to increase the wall thicknessof such expansible chamber 32 so as to withstand the pressure and tolimit its expansion since it has no casing to confine it. Also it hasbeen found desirable to make such resilient expansion chamber 32 of ovalshape, as shown particularly in FIGS. 8 and 10, rather than of tubularconfiguration. This oval shape thus allows the expansion chamber toexpand more in one plane than the other and thus approach a cylinder, asshown by the dotted lines in FIG. 10, and in addition allows theinjected swirling smoke powder to circulate and build up in pressure inthe resilient expansion chamber 32 from which it then flows to thecoating manifolds through the conduits 19 and 20 in the same manner aspreviously described relative to FIGS. 1 to 6. Upon completion of thecoating cycle the cylindrical expansion chamber 32 collapses to itsoriginal oval shape thus dislodging any accumulated powder agglomeratesin identically the same manner as the collapse of the tubular insert 14.

It should thus become obvious to those skilled in the art that anelectrostatic coating apparatus is herein shown and described in whichthe formation of powder agglomerates is minimized by the provision of aflexible expansion chamber of a resilient dielectric material. By theutilization of dielectric material for the expansion chamber thebuilding-up of an electrostatic charge on the chamber wall issubstantially eliminated. Moreover, the collapse of such chamber upontermination of each coating cycle causes dislodgment of any powder thatdoes tend to accumulate on the chamber wall thus eliminating theformation of powder agglomerates which would otherwise aflect thedensity of the powder applied to the electric lamp bulbs being coated.

Although several embodiments of the present invention have been shownand described it is to be understood that still further modificationsthereof may be made without departing from the spirit and scope of theappended claims.

We claim:

1. A device for delivering powder smoke to an electrostatic coatingapparatus comprising:

(a) a smoke generator for suspending the powder particles in a gaseousmedium and cyclically delivering the powder smoke therefrom,

(b) an expansion chamber connected to said smoke generator for buildingup the volume of the powder smoke cyclically introduced into saidchamber from said generator, said expansion chamber comprising aflexible material expansible under pressure of the powder smokeintroduced therein and operable to cause dislodgment of accumulatedpowder agglomerates from the wall thereof upon the collapse of saidflexible expansion chamber following each bulb coating cycle,

(c) and a conduit extending from said expansion chamber for thetransmission of said powder smoke to said electrostatic coatingapparatus.

2. A device for delivering powder smoke to an electrostatic coatingapparatus comprising:

(a) a smoke generator for suspending the powder particles in a gaseousmedium and cyclically delivering the powder smoke therefrom,

(b) an expansion chamber connected to said smoke generator for buildingup the volume of the powder smoke cyclically introduced into saidchamber from said generator, said expansion chamber comprising aflexible dielectric material expansible under pressure of the powdersmoke introduced therein to prevent build-up of an electrostatic chargeotherwise causing the accumulation of powder agglomerates on the wall ofsaid expansion chamber and for dislodging powder accumulation upon thecollapse of said flexible expansion chamber following each bulb coatingcycle,

(c) and a conduit extending from said expansion chamber for thetransmission of said powder smoke to said electrostatic coatingapparatus.

3. A device for delivering powder smoke to an electrostatic coatingapparatus comprising:

(a) a smoke generator for suspending the powder particles in a gaseousmedium and cyclically delivering the powder smoke therefrom,

(b) an expansion chamber connected to said smoke generator for buildingup the volume of the powder smoke cyclically introduced into saidchamber from said generator, said expansion chamber comprising acoaxially disposed insert of flexible material expansible under pressureof the powder smoke introduced therein into contact with the interiorwall of said expansion chamber and said insert being operable todislodge powder accumulation upon the collapse of said flexible insertto its normal contour following each bulb coating cycle,

(c) and a conduit extending from said expansion chamber for the cyclictransmission of said powder smoke to said electrostatic coatingapparatus.

4. Apparatus for receiving periodically generated pulses of smokecomprising powdered material suspended in a gaseous stream, and forevenly distributing the powdered material in each pulse of the smoke fordelivery to a powder coating outlet, while simultaneously preventing theaccumulation of powder deposits which might be introduced into alater-received pulse of such smoke, said apparatus comprising:

(a) expansion chamber means for receiving each said periodicallygenerated smoke pulse and expanding the gas in each such pulse to evenlydistribute the powder in the gaseous stream comprising each receivedsmoke pulse, said expansion chamber means formed of resilient materialwhich is normally in contracted position but which will expand when asmoke pulse is introduced therein;

(b) smoke pulse feed means opening into said expansion chamber means forintroducing therein each said periodically generated smoke pulse;

(c) outlet means opening from said expansion chamber means to conducteach expanded smoke pulse away from said expansion chamber means to saidpowder coating outlet;

(d) depositedapowder outlet means positioned at the lower portion ofsaid expansion chamber means for removal of any powder which mightdeposit within said expansion chamber means; and

(e) actuating means for closing said deposited powder coating outletduring the period each said smoke pulse is received in said expansionchamber means, and said actuating means opening said deposited powderoutlet means when said expansion chamber means is in normal contractedposition to permit any powder remaining in said expansion chamber meansto pass through said deposited powder outlet means.

References Cited by the Examiner UNITED STATES PATENTS MORRIS KAPLAN,Primary Examiner.

1. A DEVICE FOR DELIVERING POWDER SMOKE TO AN ELECTROSTATIC COATINGAPPARATUS COMPRISING: (A) A SMOKE GENERATOR FOR SUSPENDING THE POWDERPARTICLES IN A GASEOUS MEDIUM AND CYCLICALLY DELIVERING THE POWDER SMOKETHEREFROM, (B) AN EXPANSION CHAMBER CONNECTED TO SAID SMOKE GENERATORFOR BUILDING UP THE VOLUME OF THE POWDER SMOKE CYCLICALLY INTRODUCEDINTO SAID CHAMBER FROM SAID GENRATOR, SAID EXPANSION CHAMBER COMPRISINGA FLEXIBLE MATERIAL EXPANSIBLE UNDER PRESSURE OF THE